CTEK Automation Control Application APN007 - Manual (Page 34)

Application Note – Automation Control Application
APN007 25 July, 2014
29
Configure Formulas
Ctek's Automation Control application provides support for user defined formulas that can be
applied to analog and numeric inputs. Formulas are applied as a part of the input processing prior
to the pin being evaluated.
A standard conversion formula is released with the firmware. In many cases this standard formula
will suffice for input processing. Users may create additional formulas using postfix notation, an
input format colloquially known as RPN or Reverse Polish Notation.
[NB. Reverse Polish pays homage to the nationality of logician Jan Łukasiewicz, who
invented (prefix) Polish notation in the 1920s. The antithesis of prefix (Polish) notation is
postfix (reverse Polish) notation.]
A simple albeit useful explanation of postfix (RPN) notation is that it is a mathematical notation
wherein every operator follows all of its operands. As an example 2 [Enter] 5 [Multiply] = 10. The
result, 10 is then pushed on the top of the stack where it becomes the next operand in line.
Therefore, 2 [Enter] 5 [Multiply] = 10 and 2 [Enter] 5 [Multiply] 7 [Multiply] = 70.
From the top level Automation Control Configuration menu selecting Formulas presents the
following selection screen which allows a user to select an existing formula for modification or
create a new formula by entering an unused formula number.
Figure 29 - Input Formula Selection Screen
Selecting a new or existing formula for edit brings up the following screen. The left hand column
provides a selection of pull-down operands. The right hand column provides a pull down selection
of operators. Constants are entered in the center column. An explanation of field selection
follows.